James h



Jan. 1 1924' H. GRAY SMELTING oREs oF Low VOLATILE METALS AND MELTING SUCH METALS Filed F'eb. 17. 1921 2 SheetS-Sheet l.

fr l/ Sinnen 'o z tt /f/M/FSH @my f 44 i u@ @f Jan. l, 1924 J. H. GRAY lSMELTING GRES OF LOW VOLATILE METALS AND MELTING SUCH METALS Filed Feb. 17, 1921 2 Sheets-Sheet 2 Patented Jan. 1, i924.

Qumran amas n. GRAY, or NEW Yonx, N. Y.

saremmo omis or Low-vermute METALS No 'mamme sUcH mans.

Application led February 17, 1921.- Serial No. 445,820. l

similar brickwork 11 between the hearth and l To all 'whom it may concern:

i Be it knownthatl I, JAMES. GnAY, a citizen of the United States, residin in the city,-county, and State of New ork,

`have invented certain new-and useful Improveniente in Smelting Ores .of Low- Volatile Metals and Melting Such Metals,

of which the following is a specification.

My invention aims to provide ar furnace and a method of generating heat .therein for the smelting of oresof low volatile `metals such as tin ore and for, the melting of such metals as tin or brass, for example. The invention is also adapted to various other similar purposes. i

In my Patent No. 1,340,951, May 25, 1920, I have described an invention applicable to the same pur oses. The arrangement in thatpatent, owever, is such that the heat is radiated largely to the roof with a damaging'eiiect thereon. According to my present invention the roof is more or less yshielded from the heat and the heat is better applied to the charge, The accompanying drawings illustrate embodiments of the invention. Fig. l is a central vertical section of a. furnace with a single pair of electrodes at the center;

Fig. 2 is a on the line 2 2;

Figa istlsecuot similar to rig. 1 of n modified construction.

Referring .to the furnace illustrated, an

horiaontal section of the same 'annular hearth l is designed to support the y,charge which may be, for-example, one ton c `-brass to be melted. The hearth is suri usual or suitable cooling box 9. Proper electrical connections are assumed for ,passing a current through the electrodes to form an arc between them and for adjusting each of the electrodes independently Yu anddown. The hearth 1 may .be made o carbon' and pitch rammed in around, a removal fioriti surrounded by briclwgorl 1 0, and, with y, ...rlr1

4 of thefurnace has a central the lower electrode.

Or the hearth 1 may be made up of a mass ,extending from the lower electrode clear to the outside Aof the furnace, of carbon and pitch molded in place as shown in Fig. 3. Instead of carbon various other refraetoryv materials such as grain magnesia ma be used for the hearth or for the hearth 1 an adjacent parts of the base. Or the hearth and other parts of the base may be 05 built up of brickwork.

In operation' the large up er electrode -will wear in such a way as to orin or maintain a liared cavity 12 in its lower end. into i which the tapered end 13 of the lower elec.- 70

trode will enter. The are will be within the cavity at or near the top of the lower,v elctrode so that the heat of the arc will be thrown down toward the base and hearth rather than upward toward the roof.` The '"5` walls of the upper electrode surrounding the cavity, and the upper end of thei lower electrode will be highly heated from thearc and will `furnishan incandescent source of heat less violent than that of an exposed arc. B

But a certain amount of air trodes ,permits the positioning of the are at f any desired height in thefurnace and also permits of controlling the length of the arc maintained between the electrodes.

The voltage used is preferably low, for

instance forty to fifty volts. yEither alternat'95 lng or direct current may bc ,used In the latter case the smaller electrode V is preferably connected so as to be negative and to wear away only about half as fast as the larger electrode. I prefer this arrange- 100 ment in order that the formation of the cavity (producml by the volatilization of the carbon in the are) may keep pacewith the oxidation of tij-e outer surface of the large electrode. Tlv. small electrode is protected 105 from oxidation by its concealment within the cavity and by the inert gases which are formed' about its end. Also, lit graphite be used for the small electrode it generally oxidines more slowly than' amorphous carbon. Hoizvevexgthe preferred practice stated may be reversed. I for the lower electro e and amorphous carbon for the. upper one. Graphite has four times the current-carrying capacity pos l sessed ,byV amorphous carbon. Consequently diameter, in addition to the fact that the' refer to use graphiter large upper electrode protects the roof from the excessive heat of the arc.

.It is poss1ble, however, to use the same fmaterial for both electrodes. The bottom electrode will then be designed of a crosssectional area which will readily carry the commonly usedl required amount of electric current, and the upper electrodeswould have a crosssectional area much 1n excess of that neceseat is not only radiated from the surface of the larger electrode pas,V above 'explained, butis also -radiated and reflected downward from the cavity therein and strongly affects the structure of -thc 'furnace surrounding the lower electrode. This portion of the furnace, therefore, is prefrablv made ofa mostrcfractory substance, such as carbon. I prefer to use the. carboni'in the form of'bricks A14.4 They are shown in Figs. l and 2 of ental shape in two courses surrounding the, lower electrode and built upon the inner edge of the hearth. -Thcsc bricks, for example, may be. of the material or electrodes, a' mixture of anthracitecoal or coke and pitch or tar.` It is possible to repair this portion 0f the furnace from time vtotime as it is burned away by lastering on- .a mixture. einarbeiten! or tar, but' I".preferto. uee'crhn placed in position. 4Garbsen Abei 'ja conductor of heat,;:these i. 'Lor1 mass o f carbonlused at this I 1 t will-abadditional lengths may bc. placed on to of it as indicated by thc junction line 15.4 he

weight of thc added piece is sufficient to electrode.

For the furnace pf Fig. l with a hearth having a capacit of one ton of molten brass a .suitable size or Vthe elcctlmles would beV eightand sixteen inches in diameter respectivel A suitable current would `be four hun red kilo'Watts at fifty volts, giving a current density of 17.5 ampcrcs per square inch inthe amorphous carbon upperelec-l trode and amperes per square inch in the graphite lower electrode.

Fig. 1 shows the. electrodes of a common form made in sections with tapered threaded As the electrodes useful as the starting point for the cavity 4 12 which is to be formed'and maintained.

Thevfurnace may be of the Stationary type with a tap hole for emptying it or may be of the tilting type in which the molten charge is poured out'over a li at any desired point of the circumference oi) the hearth. Asingle phase furnace may be .used with one pair Vof electrodesns shown, one. lmultiple phase sorb `VaA considerable quanttya'f' heat and transfer it ,tog the` inner ,side of the hearth Anea rlyimmovable. f'lhe lower electrode may be replaced when r'minifg in a new bottom.

0r E 1 nl 9ft'hlemde amas-Ore F @News body of car-mn wed `preferred to maintain such conditions that furnace with a 'corresponding number of pairs of electrodessuitablygrouped. 'llhe lhottest part of the cavity is at. the

upper end whfwh -is mostremote imm the,

surrounding .air within the furnace and which is surrounded by the heaviest art of the top`lel'ectrode. By reason of this te1ulet-the are itself will. occur and be aintai'ned in the upper part 'of the cavity,-

even though at times the space to be bridged- .there is greater than at the'sides. The can.

bonuvapor formed and partly imprisoned at this point is quite conductive so that. a fairly long arcy may be maintained. It YWill be understood thatv the cavity shown in the drawings may be considerably changed in shape by ythe conditions of operation. It is the eavityyvvill be deeppenough to .giri

arranca becoming incandescent, furnishes an excellent heatin medium.

Though l have described with great particularity of detail certain embodiments of my invention yet it is not lo be understood that the invention is limited to the particular embodiments disclosed. Various modifications in the details and arrangement o the parts of the furnace andV in the steps of the process may be made by those skilled in the art without departure from the invention as defined in the following claims.

1. The method of providing a heat for smelting ores of low volatile metals and similar purposes which consists in maintaining an arc between two vertical electrodes of different diameters so that the upper electrode will direct the heat of the arc downward toward the charge.

2. The method of providing heat for smelting ores of low volatile metals and similar purposes which consists in maintaining a cavity in one electrode with the end of an opposite electrode in said cavity and an are between the electrodes shielded by the walls of the cavity.

3. The method of providing heat for smelting ores of low volatile metals and similar purposes which consists in maintaining a cavity in the lower end of an upper ectrode with the upper end oi a lower elecade projecting into 'said cavity and an are between said electrodes.

4. The method of providing heat for smelting ores of low volatile metals and similar purposes which consists iny maintaining an arc between two electrodes of different diameters, the material of the larger ele-ctrode having a. lower current-carrying capacity than that of the smaller electrode.

5. The method of providing heat for smelting ores of low volatile metals and similar purposes which consists in maintainingan arc between two electrodes of difiercnt diameters, the larger electrode being of amorphous carbon and the smaller electrode of graphite.

6 3. ,si furnace For smelting ores ol low volatile metals and similar purposes comprising a hearth Vtor the charge and vertically disposed electrodes of different diameters arranged to maintain an are between them, the electrode of larger diameter being adapted to shield the roof of the furnace from the are.

7. A furnace for smelting ores of low rolatile metals and simiiar purposes comprising a hearth for the charge and electrodes ol different diameters, the smaller electrode adapted to enter a cavity in the larger and to maintain an arc between them und within such cavity, the end of the inner electrode being protected from oxidation by the inert gases within the cavity.

8. A furnace for smelting ores of low volatile metals and similar purposes comprising a hearth for the charge and upper and lower electrodes, the upper being of larger diameter and the lower being of smaller diameter and adapted to enter a cavity in the upper and to maintain an arc between them and within such cavity.

9. A VFurnace for smelting ores of low volatile metals and similar purposes comprising a hearth for the charge and electrodes of different diameters arranged to maintain an arc between them, the material of the larger electrode having a lower current-carrying capacity than that of the smaller electrode.

10. A furnace for smeltng ores of 10W volatile metals and similar purposes comprising a hearth for the charge and electrodes of different diameters 'arranged to maintain an are between them, the larger electrode being of amorphous carbon and the smaller of graphite.

1l. A furnace for smelting ores of low volatile metals and similar purposes, said furnace having a hearth and a part formed with a cavity opening downward and means for maintaining an electric arc in said cavity.

l2. A furnace for smelting ores of low volatile metals and similar pur oses, said furnace having a hearth and aving an electrode with a cavity within its end in which the are is enclosed and maintained so that the Surrounding portion of the electrode is highly heated and serves as a heating medium Jfor the charge.

i3. A furnace for smelting ores of low volatile metals and similar purposes, said furnace having a hearth and a downwardly rojecting electrodeY with a cavit in its ower end and an upwardly projecting electrode forming with the first electrode an arc in said cavity, so that the electrodes are heated by said are and form a heating medium for the charge.

14. A furnace for smelting ores of low volatile metals and similar purposes, said furnace having a hearth and a. art formed with a cavity opening downwar and means for maintaining an electric arc in said cavity, and having a part composed of conclue tive material exposed'to the heat from said 'arc and arranged to conduct such heat to the hearth.

15. A furnace for smelting ores of low volatile metals and similar purposes comprising a hearth for the charge and an electrode passing throu h the bottom of the furnace the portion o the bottom surrounding said 7electrode being of highly refractory material which is renewable from time to time by the addition of similar material to the top of the :exposed surface.

16. A furnace for smelting ores of low volatile metals and similar purposes coinprising a hearth for the charge and an electrotle passing through the bottoni ot' the furnace, the portion of the bottom surrounding said electrode being formed in its upper part of bricks of highly refractory material so that as this portion wears it can he re- -newed by the addition of new bricks at the top.

17. A furnace for smelting: ores of low volatile metals and similar purposes roulprising an annular hearth composed o'l' can bon, and an electrode for supplyingjr current to the furnace surrounded hy said annular hearth.

18. A furnace for smelting ores of low volatile metals and similar purposes romprising an annular' hearth composed of carbonmolded n position with the aid of a binder, and an electrode surrounded by said hearth, said electrode supplying the heating current to the furnace.

19. A furnace for smelting ores of low volatile metals and similar purposes comi prising a hearth and an electrode for supplyin.;r the heating current to the furnaee passing up through the` bottom of the furnace, the hank of the hearth being of carbon and forming practically a part of the electrode.

20. A furnace for sluelting oros of low volatile metals and similar purposes Colnprising a hearth formeel of conductive material and upper and lower electrodes between which an are is struck the lower eleotrode projecting ahove the general level of the hearth into the furnace.

ln witness whereof, I have hereunto signed my name.

JAMES H. GRAY. 

